Gas generator of thin-walled structure

ABSTRACT

The gas generator according to the present invention is characterized by a combustion chamber formed with a combustor cup (14) having an annular top wall fixed at an inner edge portion thereof to a circumferential edge of a top wall of a central cylindrical holder (4) by riveting (28). A combustor plate (16) is welded at an outer edge thereof to an inner edge portion of a longitudinal extension of the combustor cup (14), and at an inner edge thereof to a bottom edge portion of the holder, so as to close the combustion chamber. A diffuser (12) is provided to cover the top wall of the central cylindrical holder (4) and the top wall of the combustor cup to form a double wall of the combustion chamber. A flange extends from the longitudinal extension of the combustion cup, the flange being welded to the inner wall of the extended portion of the diffuser to form a filter/cooling chamber.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a gas generator having a thin-walledstructure for an expandable air bag for protecting the occupant(s) of anautomobile, and more particularly to an improvement in a housing of agas generator suitably incorporated in a steering wheel to protect adriver of a passenger car when the collision of the car occurs.

2. Background of the Invention

As generally known, an air bag is a conventional safety device that isprovided in a passenger car to protect a driver or passengers from animpact occurring when the car crashes. It comprises an air bag, and agas generator for inflating the air bag in a very short period of time.

This gas generator has, as main constituent elements, a centrallypositioned igniter in which a squib/enhancer is held, a cylindricalcombustion chamber, formed so as to surround the igniter, housing gasgenerants therein, and a cross-sectionally rectangular filter/coolantchamber formed axially about the combustion chamber so that a gasgenerated in the combustion chamber passes through a filter and acoolant and flows through gas outlet ports formed in the side wall ofthe filter/coolant chamber and into an air bag.

Various types of structures of a housing for forming a combustionchamber and a filter/coolant chamber in such a gas generator haveheretofore been proposed.

For example, Japanese Patent Publication-A No. 155857/1990 proposes agas generator in which a combustion chamber is formed by a combinationof a bottomed cylindrical portion of a housing body and a cover memberwelded to an opened part of this cylindrical portion so as to minimizethe dimensions and weight of the gas generator.

Japanese Patent Publication-A No. 152639/1980 discloses a gas generatorof a thin-walled structure formed so as to reduce the weight of acasing, in which a combustion chamber and a filter chamber are formed bya combination of a central cylinder in which an igniter is held, acover, and an S-shaped casing. Outlet ports of the filter chamber(expansion chamber) being made in the form of slits by punching anextended portion of the casing.

However, when any of these conventional gas generators of a thin-walledstructure are incorporated in a steering wheel of an automobile, safetyproblems arise since the wall of the housing which faces a driverconsists of one thin plate covering a combustion chamber. Moreover,another disadvantage is that an assembly line for such gas generators,and the relative equipment used becomes complicated since the sealing ofhousings for the gas generants is done by welding.

An object of the present invention is to provide a gas generator of aweight-reduced, thin-walled structure having a housing of improvedstrength, capable of sealing gas generants by a non-welding method,which is advantageous with respect to the manufacturing equipmentrequired.

SUMMARY OF THE INVENTION

Namely, the present invention relates to a gas generator of athin-walled structure, having a central cylindrical holder 3 in which asquib/enhancer is housed, a combustion chamber surrounding the holderand holding gas generants therein, a filter/coolant chamber formedannularly so as to surround the combustion chamber adapted to allow theentry thereinto of a gas from the combustion chamber, and gas outletports from said filter/coolant chamber through which the gas may enterinto an air bag. The apparatus of the present invention is characterizedin that the combustion chamber 10 is formed with a combustor cup 14having an annular top wall fixed at an inner edge portion thereof to acircumferential edge of a top wall of the central cylindrical holder 4by riveting. At the lower end of the combustion chamber 10, a combustorplate 16 is welded at an outer edge thereof to an inner edge portion ofa longitudinal extension of the combustor cup, and the combustor plate16 is welded at an inner edge thereof to an edge portion of the centralcylindrical holder 3, so as to close the combustion chamber. A diffuser12 is provided to cover the top wall of the combustion chamber whereby adouble wall for the combustion chamber is formed. An extended portion ofthe diffuser and the flange at the outer circumference of the combustorcup form the filter/coolant chamber, a free end portion of the flange atthe outer circumference of the combustor cup being welded to the innerwall of the extended portion of the diffuser. The outlet ports for a gasflowing from the filter/coolant chamber are provided in the extendedportion of the diffuser.

In the gas generator according to the present invention, a circularplate constituting a diffuser is laminated on the annular top wall ofthe combustion cup and the top wall of the combustion chamber to form adouble wall for the combustion chamber. Therefore, the combustionchamber is doubly constructed, and an advantageous effect concerning thesafety of the device is obtained. Since an expansion chamber(filter/coolant chamber) is formed by a combination of an extendedportion of the diffuser and a flange at the outer circumference of thecombustor cup, press working can be utilized, so that this part can beproduced more easily and more inexpensively than by forging. In order toform a housing of the gas generator according to the present invention,a central holder has a combustor plate (cover member) which is weldedthereto. The outer circumferential portion of the combustor plate iswelded to a longitudinal extension of the combustor cup to form acombustion chamber. Gas generants are placed in this combustion chamber.An upper end portion of the combustor cup is then bent by press workingand fastened to a head portion of a central holder by riveting so as toseal the gas generants in the combustion chamber by a non-weldingmethod.

According to the housing structure of the present invention, the weightthereof can be reduced owing to the employment of a thin-walledstructure of aluminum and the like, which can be produced by pressworking. Moreover, the gas generants can be sealed by a non-weldingmethod. This enables an assembly line, and the equipment used, to besimplified.

When the housing structure of the gas generator according to the presentinvention is employed, the following effects can be obtained:

(1) The portion of the combustion chamber facing the passengers of anautomobile is doubly formed, so that the gas generator is advantageouswith respect to the safety thereof.

(2) Since the sealing of the gas generants can be done by a non-weldingmethod, an assembly line and the equipment used can be simplified.

(3) Owing to the thin-walled structure, the weight of the gas generatorcan be reduced, and, since press working can be employed, this gasgenerator can be manufactured more efficiently and more inexpensivelythan a gas generator manufactured by forging.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings in which:

FIG. 1 is a schematic longitudinal section of an embodiment of the gasgenerator according to the present invention.

DETAILED DESCRIPTION

The details of the present invention will now be described on the basisof an embodiment thereof shown in the drawing.

FIG. 1 is a sectioned side elevation of the gas generator according tothe present invention for an air bag for protecting the occupants of anautomobile.

A gas generator 2 covered at its upper portion with a folded expandableair bag (not shown) cooperates with a collision sensor (not shown) toform a safety device for protecting the occupants of an automobile. Thissafety device is held in a steering wheel of an automobile.

The gas generator 2 has a central cylindrical holder 4 housing asquib/enhancer in the central portion thereof. After the squib/enhancerhas been inserted in the holder 4, the lower end portion 3 of the holderis caulked (shown by a reference numeral 3) and connected to a collisionsensor through conductors 5. The inner circumferential edge of anannular combustor plate (cover member) 16, which forms a bottom wall ofa combustion chamber 10, is then welded to the outer circumferentialedge of the lower end portion of the holder 4 at 30. The outercircumferential edge of annular combustor plate 16 is attached to theinner circumferential portion of a longitudinal extension of unprocessedcylindrical combustor cup 14, at 32 to form the combustion chamber 10,in which a required number of disc type gas generants 13 are positioned.The upper end portion of the combustor cup 14 is then bent by pressworking and fastened to the head portion of the central holder 4 byriveting 28 to seal the gas generants in the combustion chamber 10. Adisc type diffuser 12 having an extended portion 11 is laminated on thetop walls of the central holder 4 and combustor cup 14 thus formed, sothat this portion of the housing of the combustion chamber is doublyformed. The extended portion 11 of this diffuser 12 and a flange 15extending from the longitudinal extension of the combustor cup 14 formsa filter/coolant chamber (expansion chamber) 18 in which a filter and acoolant are provided. The outer circumferential edge of the flange 15 iswelded to the inner circumferential edge of the lower end portion of thedownwardly suspended extended portion of the diffuser 12, at 34. Acombustion gas is produced from the gas generants 13 ignited by anigniter 6 in the holder 4 through the openings 7 provided in thecircumferential wall of the holder. The generated gas flows into theexpansion chamber 18 through a plurality of communication ports 9provided in the longitudinal extension of the combustor cup 14, andpasses through a coolant 26 and a filter 20. The resultant gas flows outof the gas generator through a plurality of gas outlet ports 21 and intoan air bag to expand the same instantaneously. A retainer 27 is providedbetween the coolant 26 and filter 20 so that gas flow is directed firstupon the coolant 26 and then passes through the filter 20.

In the housing of the gas generator according to the present invention,the central cylindrical holder 4, combustor plate 16, combustor cup 14and diffuser 12 are joined to one another via annular welding seams 30,32, 34 by electron beam welding or laser beam welding, whereas the topwall of the combustor is attached by riveting 28 to the central holder 4after the completion of the insertion of the gas generant 13 into thecombustor cup 14.

What is claimed is:
 1. A gas generator of a thin-walled structure,having a central cylindrical holder in which a squib or enhancer ishoused, a combustion chamber surrounding said holder and holding gasgenerants therein, a filter and coolant chamber formed annularly so asto surround said combustion chamber, and adapted to allow the entrythereinto of a gas which has passed through openings thereofcommunicating with said combustion chamber, and gas outlet ports formedat said filter and coolant chamber and through which the gas which haspassed through a filter and a coolant rushes into an air bag,characterized in that said combustion chamber (10) is formed with acombustor cup (14) having an annular top wall fixed at an inner edgeportion thereof to a circumferential edge of a top wall of said centralcylindrical holder (4) by riveting, a combustor plate (16) being weldedat an outer edge thereof to an inner edge portion of a flange at anouter circumference of said combustor cup, and at an inner edge thereofto an opposite edge portion of said holder, so as to close saidcombustion chamber, a diffuser (12) being provided so as to cover saidtop wall of said central cylindrical holder and a top wall whichcontinues therefrom of said combustor cup, whereby a double wall forsaid combustion chamber is formed, an extended portion of said diffuserand said flange at the outer circumference of said combustor cup formingsaid filter and coolant chamber, a free end portion of said flange atthe outer circumference of said combustor cup being welded to the innerwall of said extended portion of said diffuser, said outlet ports for agas flow from said filter and coolant chamber being provided in saidextended portion of said diffuser.
 2. A gas generator comprising:ahousing having a top portion, a bottom portion, an igniter means mountedtherein and means for communicating with the interior of said housing; acombustion chamber surrounding said housing, said combustion chamberformed by a top wall and a bottom wall, said top wall having an innerend and an outer end, said inner end affixed to said top portion of saidhousing and said outer end extending to form a flange portion, saidbottom wall having an inner edge and an outer edge, said inner edgeaffixed to said bottom portion of said housing and said outer edgeaffixed to said flange portion, said combustion chamber communicatingwith said communicating means; a diffuser member positioned to coversaid top portion of said housing and said top wall of said combustionchamber and terminating in an extension portion having an outlet, saiddiffuser member and said top wall forming a double wall over saidcombustion chamber; and a filter and coolant chamber surrounding saidcombustion chamber and communicating therewith, said filter and coolantchamber formed by affixing said flange portion of said top wall to saidextension portion of said diffuser member.
 3. The gas generatoraccording to claim 2, wherein said top wall is annular and said topportion is formed with a circumferential edge for being affixed to saidinner end of said top wall.
 4. The gas generator according to claim 2,wherein said bottom wall is a combustor plate with said inner edgewelded to said bottom portion of said housing and said outer edge weldedto said flange portion.
 5. The gas generator according to claim 2,wherein said flange portion includes a free-end portion, said free-endportion being welded to said extension portion of said diffuser member.6. The gas generator according to claim 2, wherein said filter andcoolant chamber includes retaining means positioned between coolant anda filter in said chamber such that gas flow is directed first upon saidcoolant before passing through said filter.
 7. The gas generatoraccording to claim 2, wherein said igniter means is a squib or enhancer.8. The gas generator according to claim 2, wherein said combustionchamber includes disc-type gas generants housed therein.
 9. The gasgenerator according to claim 2, wherein said diffuser member islaminated at said top portion of said housing and said top wall of saidcombustion chamber.
 10. The gas generator according to claim 2, whereinsaid diffuser member is a disc-type diffuser.
 11. The gas generatoraccording to claim 2, wherein said outlet communicates with an air bagto be inflated by said generator.
 12. A gas generator comprising:ahousing having a top portion, a bottom portion, an igniter means mountedtherein and means for communicating with the interior of said housing; acombustion chamber surrounding said housing, said combustion chamberformed by a top wall and a bottom wall, said top wall having an innerend and an outer end, said inner end riveted to said top portion of saidhousing and said outer end extending to form a flange portion, saidbottom wall having an inner edge and an outer edge, said inner edgeaffixed to said bottom portion of said housing and said outer edgeaffixed to said flange portion, said combustion chamber communicatingwith said communicating means; a diffuser member positioned to coversaid top portion of said housing and said top wall of said combustionchamber and terminating in an extension portion having an outlet, saiddiffuser member and said top wall forming a double wall over saidcombustion chamber; and a filter and coolant chamber surrounding saidcombustion chamber and communicating therewith, said filter and coolantchamber formed by affixing said flange portion of said top wall to saidextension portion of said diffuser member.
 13. The gas generatoraccording to claim 12, wherein said top wall is annular and said topportion is formed with a circumferential edge for being riveted to saidinner end of said top wall.
 14. The gas generator according to claim 12,wherein said bottom wall is a combustor plate with said inner edgewelded to said bottom portion of said housing, and said outer edgewelded to said flange portion.
 15. The gas generator according to claim12, wherein said flange portion includes a free-end portion, saidfree-end portion being welded to said extension portion of said diffusermember.
 16. The gas generator according to claim 12, wherein said filterand coolant chamber includes retaining means positioned between coolantand a filter in said chamber such that gas flow is directed first uponsaid coolant before passing through said filter.
 17. The gas generatoraccording to claim 12, wherein said combustion chamber includesdisc-type gas generants housed therein.
 18. The gas generator accordingto claim 12, wherein said diffuser member is laminated at said topportion of said housing and said top wall of said combustion chamber.19. The gas generator according to claim 12, wherein said diffusermember is a disc-type diffuser.
 20. The gas generator according to claim12, wherein said outlet communicates with an air bag to be inflated bysaid generator.